I did not have Swizzler at the game today (almost always eat outside the park before games to either save money or get better food for the same cost), but I have gone to their location on 1st Street SE about four times (work nearby). Their burgers are very good, not quite as good as Shake Shack but similar in style (and IMO better than Five Guys), and the cost is a few dollars less than Shake Shack or Five Guys if you get a combo. (The fries are good but unspectacular IMO.)

Saying the above more simply, Swizzler is a solid option at Nationals Park, though like Shake Shack I think eating at the location outside but near the ballpark makes more sense. The non-ballpark location is a few dollars less and doesn’t have the sports event/captive customer markup.